Directed display architecture

ABSTRACT

A head mounted display (HMD) includes an electronic display, a microlens array, and an optics block. The electronic display is composed of a plurality of sub-pixels, and each sub-pixel is configured to emit image light according to respective emission distribution. The microlens array is coupled to the electronic display and includes a plurality of microlenses. The microlens array concentrates the emission distributions of the sub-pixels to form concentrated image light and directs the concentrated image light towards a target region. The optics block is positioned in the target region. The optics block is configured to direct the concentrated image light from the microlens array to an exit pupil of the HMD corresponding to a location of an eye of a user of the HMD.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application No. 62/343,282 filed on May 31, 2016, the content of which is incorporated by reference in its entirety herein.

BACKGROUND

The present disclosure generally relates to electronic displays, and specifically relates to directed electronic displays in head-mounted displays (HMDs).

Conventional display technology is designed to have a large viewing angle. This is usually done by designing the display to act as a Lambertian source. A Lambertian source is defined as a source whose emission distribution is such that the apparent brightness (or luminance) is independent of angle—in other words, the off-axis luminance is the same as the on-axis. A Lambertian source (or a source with a similar emission distribution) helps minimize any variation in emitted optical light as a function of viewing angle. This is quite useful for traditional consumer electronics that are designed to be used in environments where viewers can be located at different positions relative to the display and the position of the viewer relative to the display does not cause large changes in apparent brightness.

But in the space of HMDs, a Lambertian emission distribution is largely a hindrance, as a viewing user is located at a specific position relative to the display. As a Lambertian emission pattern is designed to emit light to maximize viewing angle, a lot of the off-axis light is wasted (as it is not being directed to eyes of the user wearing the HMD, notionally located in a region defined as the “eyebox”), and therefore power used to generate the light is also wasted. Moreover, the wasted light introduces a potential for stray light, as the wasted light can scatter within the HMD and reduce the apparent contrast of media being presented by the HMD.

Moreover, HMDs may magnify an internal display to, e.g., increase a field of view for the viewing user. However, conventional displays are traditionally not meant for magnified viewing (above normal unaided vision perception limits). Accordingly, the increased magnification (versus unaided viewing) of a conventional display in a HMD can lead to the viewing user seeing the “dead-space” between the emission points of the display, which causes a “pixelated” or “screen-door” effect under use.

SUMMARY

A directed display concentrates emission distributions of sub-pixels and/or pixels towards a target region. The directed display includes an electronic display element and a microlens array that is directly affixed to the electronic display element. The microlens array includes a plurality of microlenses, and is affixed such that each microlens concentrates an emission distribution from a corresponding single sub-pixel (or pixel in some embodiments). Concentration of an emission distribution tightens an emission distribution (i.e., decreases a solid angle describing the emission distribution from a corresponding sub-pixel). Additionally, concentration of an emission distribution directs an emission distribution of a corresponding sub-pixel towards the target region. For example, concentrated emission distributions for sub-pixels along a periphery of the electronic display element are directed toward the target region, thereby increasing the amount of light emitted by the sub-pixel that makes it to the target region. In this manner, a larger percentage of light emitted from sub-pixels and/or pixels is received at the target region than would otherwise be received if no concentration of the emission distribution occurred (e.g., no microlens array). Therefore, concentration of the emission distributions causes a net increase in power of the light that reaches a viewing user, helps to hide the “screen door” effect by magnifying the apparent size of the emission area to optically fill in the dead-space (related to etendue conservation, when the emission angle is decreased), reduces potential for stray-light (i.e., light not reaching the target region that continues to scatter within the system), and allows a better uniformity across the display (as pixels near the edge are more closely matched in brightness to those near the center). Accordingly, concentration of the emission distribution results in more of the emitted light reaching the target region and preventing adverse scene conditions otherwise.

In the context of an HMD that includes an electronic display element, a microlens array, and an optics block. The electronic display element outputs image light via sub-pixels having different colors. The sub-pixels are separated from each other by a dark space region (to fit associated electronics primarily, but can be purposefully tuned with this embodiment), and the sub-pixels have associated emission distributions that describe ranges of angles of light emitted from the plurality of sub-pixels. The microlens array includes microlenses that are each coupled to at least one corresponding sub-pixel of the sub-pixels. The microlenses concentrate the emission distributions and direct the emission distributions toward a target region. The optics block is located in and around the target region, and the optics block is configured to optically correct the image light, and direct the optically corrected image light from the microlens array to an exit pupil of the HMD corresponding to a defined eyebox and the location of an eye of a user of the HMD.

There exists a trade-off between allowed brightness increase versus the ratio of the emission area versus dark space region to be “filled in.” On one extreme, the microlenses can allow maximum brightness (up to completely optically filling in the dark space region) to reach the user while preserving a desired minimum eyebox size (usually equal to or larger than the human pupil diameter, notionally on the order of 10 millimeters). Here, the gain in brightness is approximated by the ratio of a unit cell dark area of a sub-pixel plus an emission area of the sub-pixel, divided by the emission area. However, as that gain is increased, the geometric and diffraction-limited eyebox size correspondingly shrink as they are related by the optical etendue of the system. On the other extreme, if the gain necessitated to reach maximum brightness to the user would result in an unacceptably small eyebox (which would imply beyond the limits of eye-tracking or no eye-tracking being involved) then it could not be fully realized and the ‘screen door’ effect would at least partially remain. To offset this, the gain would be set to the maximum brightness, and then diffusing optical elements would be introduced to the microlens architecture to work around the etendue limit and maintain the necessary eyebox size (while fully mitigating the screen-door effect). Accordingly, in some embodiments, the microlenses are engineered diffusing microlenses that generate blur spots in the image light that both mask the dark space region between adjacent sub-pixels and present a specified “eyebox” size. A blur spot corresponding to a blurred image of a sub-pixel in the image light. In this manner, the microlenses are able to compensate for the screen-door effect while providing for the specified eyebox conditions.

In one embodiment, the electronic display element outputs image light via groups of sub-pixels. The groups of sub-pixels are separated from each other by a first dark space region, and the sub-pixels within each group are separated from other sub-pixels of the same group by a second dark space region, where the second dark space region is smaller than that of the first dark space region. For example, the second dark space region may be so small that the sub-pixels within a group of sub-pixels are place right next to each other such that the adjacent sub-pixels abut each other.

In one embodiment, a head mounted display (HMD) includes an electronic display, a microlens array, and an optics block. The electronic display is composed of a plurality of sub-pixels, and each sub-pixel is configured to emit image light according to respective emission distribution. The microlens array is coupled to the electronic display and includes a plurality of microlenses. The microlens array concentrates the emission distributions of the sub-pixels to form concentrated image light and directs the concentrated image light towards a target region. The optics block is positioned in the target region. The optics block is configured to direct the concentrated image light from the microlens array to an exit pupil of the HMD corresponding to a location of an eye of the user of the HMD.

In one embodiment, a directed display comprises an electronic display and a microlens array. The electronic display is composed of a plurality of sub-pixels and each sub-pixel is configured to emit image light according to respective emission distribution. The microlens array is coupled to the electronic display and includes a plurality of microlenses. The microlens array is configured to concentrate the emission distributions of the sub-pixels to form concentrated image light and direct the concentrated image light towards a target region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a system environment including a virtual reality system, in accordance with an embodiment.

FIG. 2A is a wire diagram of a virtual reality (VR) headset, in accordance with an embodiment.

FIG. 2B is a cross section of the front rigid body of the embodiment of a VR headset shown in FIG. 2A

FIG. 3A illustrates a cross section of a sub-pixel emitting light, according to an embodiment.

FIG. 3B illustrates a cross section of the sub-pixel shown in FIG. 3A and a corresponding microlens, according to an embodiment.

FIG. 4 illustrates a cross section of a directed display, according to an embodiment.

FIG. 5A illustrates a diffuser microlens coupled to a sub-pixel, according to an embodiment.

FIG. 5B illustrates an example of a sub-pixel coupled to a diffuser microlens including a waveguide structure, according to an embodiment.

FIG. 5C illustrates an example of a sub-pixel coupled to a diffuser microlens that includes a waveguide structure and a plurality of diffusing features, according to an embodiment.

FIG. 5D illustrates another example of the sub-pixel coupled to a diffuser microlens including internal diffusing features, according to an embodiment.

FIG. 5E illustrates an example cross section of an electronic display element coupled to a microlens array, according to one embodiment.

FIG. 5F illustrates another example cross section of an electronic display element coupled to a microlens array, according to one embodiment.

FIG. 5G illustrates yet another example cross section of an electronic display element coupled to a microlens array, according to one embodiment.

FIG. 6A is an example array of sub-pixels on the electronic display element.

FIG. 6B is an example of image light emitted by an array of sub-pixels and adjusted by a microlens array and an optics block, according to an embodiment.

FIG. 7A illustrates a cross-section of a directed display with a single microlens for each set of an example array of sub-pixels, according to one embodiment.

FIG. 7B illustrates a cross-section of a directed display with a single microlens for each set of an example array of sub-pixels, where the example array of sub-pixels are grouped to improve the quality of image light incident upon a target region, according to an embodiment.

The figures depict embodiments of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles, or benefits touted, of the disclosure described herein.

DETAILED DESCRIPTION

System Overview

FIG. 1 is a block diagram of a virtual reality (VR) system environment 100 in which a VR console 110 operates. The system environment 100 shown by FIG. 1 comprises a VR headset 105, an imaging device 135, and a VR input interface 140 that are each coupled to the VR console 110. While FIG. 1 shows an example system 100 including one VR headset 105, one imaging device 135, and one VR input interface 140, in other embodiments any number of these components may be included in the system 100. For example, there may be multiple VR headsets 105 each having an associated VR input interface 140 and being monitored by one or more imaging devices 135, with each VR headset 105, VR input interface 140, and imaging devices 135 communicating with the VR console 110. In alternative configurations, different and/or additional components may be included in the system environment 100. Similarly, functionality of one or more of the components can be distributed among the components in a different manner than is described here. For example, some or all of the functionality of the VR console 110 may be contained within the VR headset 105.

The VR headset 105 is a head-mounted display that presents media to a user. Examples of media presented by the VR headset 105 include one or more images, video, audio, or some combination thereof. In some embodiments, audio is presented via an external device (e.g., speakers and/or headphones) that receives audio information from the VR headset 105, the VR console 110, or both, and presents audio data based on the audio information. Some embodiments of the VR headset 105 are further described below in conjunction with FIGS. 2 and 3. The VR headset 105 may comprise one or more rigid bodies, which may be rigidly or non-rigidly coupled to each other together. A rigid coupling between rigid bodies causes the coupled rigid bodies to act as a single rigid entity. In contrast, a non-rigid coupling between rigid bodies allows the rigid bodies to move relative to each other. In some embodiments, the VR headset 105 may also act as an augmented reality (AR) headset. In these embodiments, the VR headset 105 augments views of a physical, real-world environment with computer-generated elements (e.g., images, video, sound, etc.).

The VR headset 105 includes a directed display 112, an optics block 118, one or more locators 120, one or more position sensors 125, and an inertial measurement unit (IMU) 130. The directed display 112 directs image light toward a target region including the optics block 118, thereby increasing power of the image light that reaches the target area, reducing potential for stray-light, and increases spatial and brightness uniformity across the display (as pixels near the edge are more closely matched in brightness to those near the center). The directed display 112 includes an electronic display 115 and a microlens array 116.

The electronic display 115 presents images to the user in accordance with data received from the VR console 110. In various embodiments, the electronic display may comprise a single electronic display element or multiple electronic display elements (e.g., a display for each eye of a user). Examples of the electronic display element include: a liquid crystal display (LCD), an organic light emitting diode (OLED) display, an active-matrix organic light-emitting diode display (AMOLED), some other display, or some combination thereof.

The electronic display 115 includes a display area comprising a plurality of sub-pixels under each unit repeating pixel structure, where a sub-pixel is a discrete light emitting component, and a pixel structure includes a plurality of the same sub-pixels (e.g., red, blue, green). Different sub-pixels are separated from each other by dark space regions. A dark space region is the portion of the display area that does not emit light. For example, a sub-pixel emits red light, yellow light, blue light, green light, white light, or any other suitable color of light. In some embodiments, images projected by the electronic display 115 are rendered on the sub-pixel level. This is distinct from, say an RGB (red-green-blue) layout, which has discrete red, green, and blue pixels (red, green, and blue) and each pixel in the RGB layout includes a red sub-pixel, which is adjacent to a green sub-pixel that is adjacent to a blue sub-pixel; the red, green, and blue sub-pixels operate together to form different colors. In an RGB layout a sub-pixel in a pixel is restricted to working within that pixel. However, in some embodiments, sub-pixels in the electronic display operate within multiple “logical” pixels in their surrounding vicinity to form different colors. The sub-pixels are arranged on the display area of the electronic display 115 in a sub-pixel array. Examples of a sub-pixel array include PENTILE® RGBG, PENTILE® RGBW, some another suitable arrangement of sub-pixels that renders images at the sub-pixel level. In some embodiments, one or more adjacent sub-pixels are of the same color.

Each sub-pixel emits light according to an emission distribution. In some embodiments, the sub-pixels have relatively broad emission distribution (e.g., a Lambertian emission distribution or something similar). An emission distribution describes a range of angles of light emitted from a sub-pixel. The emission distribution can be quantified in terms of solid angle. A solid angle is a 3 dimensional analog of an ordinary angle such as that subtended by a cone and is measured in steradians. To estimate the percentage of light that is effectively collected by an observer's eye, one can consider, as an example, an observer with an eye pupil diameter of 4 mm. Assuming a focal length of 40 mm for the collimating optics, the half angle of the solid angle that is effectively collected by the eye is approximately 0.05 Radians (i.e., (4 mm/40 mm)*½). Assuming the display to be close to a Lambertian emitter, the portion of light effectively collected by the eye is about 0.25% (i.e., sine square of the half angle). Therefore, increasing the directionality of the display may considerably improve the brightness of the image.

The microlens array 116 includes a plurality of microlenses that direct light emitted from the electronic display 115 toward the optics block 118. In some embodiments, the microlens array 116 is affixed directly to the display area of the electronic display 115. Additionally, in some embodiments, the microlens array 116 may be fabricated as part of the electronic display 115. Alternatively, in some embodiments, the microlens array 116 is affixed to the display area of the electronic display 115 through a microlens array spacer as described below with regard to FIGS. 5E and 5F.

The microlens is positioned relative to the electronic display 115 such that for a single microlens, the microlens receives light from a single corresponding sub-pixel. Also, in some embodiments, a microlens is positioned relative to the electronic display 115 such that the microlens receives light from a pixel.

The microlenses are shaped to reduce the solid angle associated with the emission distributions of corresponding sub-pixels. A reduction in solid angle corresponds to a tighter (e.g., more collimated) emission distribution. Due to optical relationships, as the emission distribution is concentrated, the apparent spatial extent of the emission area is seen to grown in size (which accounts for optically filling in the ‘screen-door’ effect). Accordingly, each microlens is essentially a light gathering tool that turns a relatively broad emission distribution (e.g., Lambertian distribution) into a relatively directional distribution pattern (e.g., more beam like), with a net apparent increase in the emission area as viewed by the user. Moreover, in some embodiments, the relative position between a microlens and its corresponding sub-pixel (or pixel) varies based on the location of the sub-pixel (or pixel) on the display panel. The variation in relative position allows microlenses to direct light from a corresponding sub-pixel (or pixel) to the optics block 118. Accordingly, the microlens array 116 concentrates emission distributions toward the optics block 118. The microlens array 116 may concentrate the emission distributions of sub-pixels to form concentrated image light and direct the concentrated image light towards a target region. Concentration of an emission distribution is the tightening of the emission distribution and directing an emission distribution towards a target region. The concentration of an emission distribution increases exitance (emitted intensity [watts/steradian]) which effectively brightens the sub-pixels as perceived by the user (potentially by over an order of magnitude). In this embodiment, the target region includes an optics block 118 which ultimately passes light to regions (i.e., eyeboxes) expected to include eyes of a user of the VR headset 105. Accordingly, concentration of the emission distributions results in more light being directed toward eyeboxes. The relative positioning of a microlens to a corresponding sub-pixel is discussed in detail below with regard to FIG. 3A-5G.

Additionally, in some embodiments, the microlenses are designed to diffuse (i.e., spread out) light emitted from the sub-pixels to generate blur spots in the image light that both facilitate masking a dark space region between adjacent sub-pixels and maintaining a specific eyebox size. An eyebox is typically specified as being equal to or larger than a human pupil diameter, notionally on the order of 10 millimeters. Additionally, in some embodiments, a specified size of an eyebox may be a range of values. For example, between 10 and 20 mm. A blur spot for a given sub-pixel is a diffused image of a sub-pixel, which cannot be compensated by a user's accommodation. Specific embodiments of microlenses that diffuse light are discussed in detail below with regard to FIGS. 5A-5G. The microlens array 116 outputs the blurred image light to the optics block 118, allowing the blurred image light to act as a pre-distortion of the image light that, when magnified by the optics block 118, corrects for fixed pattern noise in the image presented to the user and maintains the spatial extent of the eyebox. Additionally, these microlenses may be relatively close to each other to achieve a “dense packing” arrangement (hexagonal or rectangular, as related to sub-pixel or pixel architecture) to maximize masking the dark space region between adjacent sub-pixels. In a dense packing arrangement there is no or very limited space (as may be utilized for support structure or light blocking features) between adjacent microlenses. The dense packing arrangement may be, e.g., hexagonal, rectangular, square, or some other shape where there is no space between adjacent microlenses (i.e., each microlens is formed in the other shape and directly abuts its adjacent microlenses). For example, microlenses in a hexagonal dense packing arrangement have hexagonal shapes and abut directly to other hexagonal microlenses.

The optics block 118 magnifies received light (e.g., the blurred image light output from the microlens array 116), corrects optical errors associated with the image light, and presents the corrected image light is presented to a user of the VR headset 105. An optical element may be an aperture, a Fresnel lens, a convex lens, a concave lens, a filter, or any other suitable optical element that affects the blurred image light. Moreover, the optics block 118 may include combinations of different optical elements. In some embodiments, one or more of the optical elements in the optics block 118 may have one or more coatings, such as partially reflective, polarization filters, and/or anti-reflective coatings.

Magnification of the image light by the optics block 118 allows the electronic display 115 to be physically smaller, weigh less, and consume less power than larger displays. Additionally, magnification may increase a field of view of the displayed media. For example, the field of view of the displayed media is such that the displayed media is presented using almost all (e.g., 110 degrees diagonal), and in some cases all, of the user's field of view. However, magnification of non-blurred image light may cause an increase in fixed pattern noise, also referred to as the “screen-door effect,” which is a visual artifact where a dark space region separating pixels and/or sub-pixels of a display become visible to a user in an image presented by the display. However, the optics block 118 magnifies blurred image light so the images of adjacent sub-pixels are distinguishable and blurred to cover the dark space region between the adjacent sub-pixels. In some embodiments, the optics block 118 is designed so its effective focal length is larger than the spacing to the electronic display 115, which magnifies the image light projected by the electronic display 115. Additionally, in some embodiments, the amount of magnification may be adjusted by adding or removing optical elements.

The optics block 118 may be designed to correct one or more types of optical error in addition to fixed pattern noise (i.e., the screen-door effect). Examples of optical error include: two dimensional optical errors, three dimensional optical errors, or some combination thereof. Two dimensional errors are optical aberrations that occur in two dimensions. Example types of two dimensional errors include: barrel distortion, pincushion distortion, longitudinal chromatic aberration, transverse chromatic aberration, or any other type of two-dimensional optical error. Three dimensional errors are optical errors that occur in three dimensions. Example types of three dimensional errors include spherical aberration, comatic aberration, field curvature, astigmatism, or any other type of three-dimensional optical error. In some embodiments, content provided to the electronic display 115 for display is pre-distorted, and the optics block 118 corrects the distortion when is receives image light from the electronic display 115 generated based on the content.

The locators 120 are objects located in specific positions on the VR headset 105 relative to one another and relative to a specific reference point on the VR headset 105. A locator 120 may be a light emitting diode (LED), a corner cube reflector, a reflective marker, a type of light source that contrasts with an environment in which the VR headset 105 operates, or some combination thereof. In embodiments where the locators 120 are active (i.e., an LED or other type of light emitting device), the locators 120 may emit light in the visible band (˜380 nm to 750 nm), in the infrared (IR) band (˜750 nm to 10 micrometers), in the ultraviolet band (10 nm to 380 nm), some other portion of the electromagnetic spectrum, or some combination thereof.

In some embodiments, the locators 120 are located beneath an outer surface of the VR headset 105, which is transparent to the wavelengths of light emitted or reflected by the locators 120 or is thin enough to not substantially attenuate the wavelengths of light emitted or reflected by the locators 120. Additionally, in some embodiments, the outer surface or other portions of the VR headset 105 are opaque in the visible band of wavelengths of light. Thus, the locators 120 may emit light in the IR band under an outer surface that is transparent in the IR band but opaque in the visible band.

The IMU 130 is an electronic device that generates fast calibration data based on measurement signals received from one or more of the position sensors 125. A position sensor 125 generates one or more measurement signals in response to motion of the VR headset 105. Examples of position sensors 125 include: one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, a type of sensor used for error correction of the IMU 130, or some combination thereof. The position sensors 125 may be located external to the IMU 130, internal to the IMU 130, or some combination thereof.

Based on the one or more measurement signals from one or more position sensors 125, the IMU 130 generates fast calibration data indicating an estimated position of the VR headset 105 relative to an initial position of the VR headset 105. For example, the position sensors 125 include multiple accelerometers to measure translational motion (forward/back, up/down, left/right) and multiple gyroscopes to measure rotational motion (e.g., pitch, yaw, roll). In some embodiments, the IMU 130 rapidly samples the measurement signals and calculates the estimated position of the VR headset 105 from the sampled data. For example, the IMU 130 integrates the measurement signals received from the accelerometers over time to estimate a velocity vector and integrates the velocity vector over time to determine an estimated position of a reference point on the VR headset 105. Alternatively, the IMU 130 provides the sampled measurement signals to the VR console 110, which determines the fast calibration data. The reference point is a point that may be used to describe the position of the VR headset 105. While the reference point may generally be defined as a point in space; however, in practice the reference point is defined as a point within the VR headset 105 (e.g., a center of the IMU 130).

The IMU 130 receives one or more calibration parameters from the VR console 110. As further discussed below, the one or more calibration parameters are used to maintain tracking of the VR headset 105. Based on a received calibration parameter, the IMU 130 may adjust one or more IMU parameters (e.g., sample rate). In some embodiments, certain calibration parameters cause the IMU 130 to update an initial position of the reference point so it corresponds to a next calibrated position of the reference point. Updating the initial position of the reference point as the next calibrated position of the reference point helps reduce accumulated error associated with the determined estimated position. The accumulated error, also referred to as drift error, causes the estimated position of the reference point to “drift” away from the actual position of the reference point over time.

The imaging device 135 generates slow calibration data in accordance with calibration parameters received from the VR console 110. Slow calibration data includes one or more images showing observed positions of the locators 120 that are detectable by the imaging device 135. The imaging device 135 may include one or more cameras, one or more video cameras, any other device capable of capturing images including one or more of the locators 120, or some combination thereof. Additionally, the imaging device 135 may include one or more filters (e.g., used to increase signal to noise ratio). The imaging device 135 is configured to detect light emitted or reflected from locators 120 in a field of view of the imaging device 135. In embodiments where the locators 120 include passive elements (e.g., a retroreflector), the imaging device 135 may include a light source that illuminates some or all of the locators 120, which retro-reflect the light towards the light source in the imaging device 135. Slow calibration data is communicated from the imaging device 135 to the VR console 110, and the imaging device 135 receives one or more calibration parameters from the VR console 110 to adjust one or more imaging parameters (e.g., focal length, focus, frame rate, ISO, sensor temperature, shutter speed, aperture, etc.).

The VR input interface 140 is a device that allows a user to send action requests to the VR console 110. An action request is a request to perform a particular action. For example, an action request may be to start or end an application or to perform a particular action within the application. The VR input interface 140 may include one or more input devices. Example input devices include: a keyboard, a mouse, a game controller, or any other suitable device for receiving action requests and communicating the received action requests to the VR console 110. An action request received by the VR input interface 140 is communicated to the VR console 110, which performs an action corresponding to the action request. In some embodiments, the VR input interface 140 may provide haptic feedback to the user in accordance with instructions received from the VR console 110. For example, haptic feedback is provided when an action request is received, or the VR console 110 communicates instructions to the VR input interface 140 causing the VR input interface 140 to generate haptic feedback when the VR console 110 performs an action.

The VR console 110 provides media to the VR headset 105 for presentation to the user in accordance with information received from one or more of: the imaging device 135, the VR headset 105, and the VR input interface 140. In the example shown in FIG. 1, the VR console 110 includes an application store 145, a tracking module 150, and a virtual reality (VR) engine 155. Some embodiments of the VR console 110 have different modules than those described in conjunction with FIG. 1. Similarly, the functions further described below may be distributed among components of the VR console 110 in a different manner than is described here.

The application store 145 stores one or more applications for execution by the VR console 110. An application is a group of instructions, that when executed by a processor, generates content for presentation to the user. Content generated by an application may be in response to inputs received from the user via movement of the HR headset 105 or the VR interface device 140. Examples of applications include: gaming applications, conferencing applications, video playback application, or other suitable applications.

The tracking module 150 calibrates the VR system 100 using one or more calibration parameters and may adjust one or more calibration parameters to reduce error in determination of the position of the VR headset 105. For example, the tracking module 150 adjusts the focus of the imaging device 135 to obtain a more accurate position for observed locators on the VR headset 105. Moreover, calibration performed by the tracking module 150 also accounts for information received from the IMU 130. Additionally, if tracking of the VR headset 105 is lost (e.g., the imaging device 135 loses line of sight of at least a threshold number of the locators 120), the tracking module 140 re-calibrates some or all of the system environment 100.

The tracking module 150 tracks movements of the VR headset 105 using slow calibration information from the imaging device 135. As further described below in conjunction with FIG. 3, the tracking module 150 determines positions of a reference point of the VR headset 105 using observed locators from the slow calibration information and a model of the VR headset 105. The tracking module 150 also determines positions of a reference point of the VR headset 105 using position information from the fast calibration information. Additionally, in some embodiments, the tracking module 150 may use portions of the fast calibration information, the slow calibration information, or some combination thereof, to predict a future location of the headset 105. The tracking module 150 provides the estimated or predicted future position of the VR headset 105 to the VR engine 155.

The VR engine 155 executes applications within the system environment 100 and receives position information, acceleration information, velocity information, predicted future positions, or some combination thereof of the VR headset 105 from the tracking module 150. Based on the received information, the VR engine 155 determines content to provide to the VR headset 105 for presentation to the user. For example, if the received information indicates that the user has looked to the left, the VR engine 155 generates content for the VR headset 105 that mirrors the user's movement in a virtual environment. Additionally, the VR engine 155 performs an action within an application executing on the VR console 110 in response to an action request received from the VR input interface 140 and provides feedback to the user that the action was performed. The provided feedback may be visual or audible feedback via the VR headset 105 or haptic feedback via the VR input interface 140.

FIG. 2A is a wire diagram of a VR headset 200, in accordance with an embodiment. The VR headset 200 is an embodiment of the VR headset 105, and includes a front rigid body 205 and a band 210. The front rigid body 205 includes one or more electronic display elements of the electronic display 115 (not shown), the IMU 130, the one or more position sensors 125, and the locators 120. In the embodiment shown by FIG. 2A, the position sensors 125 are located within the IMU 130, and neither the IMU 130 nor the position sensors 125 are visible to the user.

The locators 120 are located in fixed positions on the front rigid body 205 relative to one another and relative to a reference point 215. In the example of FIG. 2A, the reference point 215 is located at the center of the IMU 130. Each of the locators 120 emit light that is detectable by the imaging device 135. Locators 120, or portions of locators 120, are located on a front side 220A, a top side 220B, a bottom side 220C, a right side 220D, and a left side 220E of the front rigid body 205 in the example of FIG. 2A.

FIG. 2B is a cross section 225 of the front rigid body 205 of the embodiment of a VR headset 200 shown in FIG. 2A. As shown in FIG. 2B, the front rigid body 205 includes a directional display 112 and an optics block 118. The directional display 112 emits directional light toward the optics block 118. Directional light is composed of light emitted from various sub-pixels and/or pixels in the directional display 112 that have concentrated emission distributions.

The directional display 112 includes an electronic display element 235 of the electronic display 115 and a microlens array 116. The electronic display element 235 emits image light, and the microlens array 116 concentrates the image light towards the optics block 118. As the light directed toward the optics block 118 is concentrated, less off-axis light is lost (as opposed to a case with no microlens array 116) and more light is ultimately directed toward the eye 245.

The optics block 118 alters (e.g., magnifies) the received light and provides it to an exit pupil 250 for presentation to the user. The exit pupil 250 is the location of the front rigid body 205 where a user's eye 245 is positioned, also referred to as the “eyebox”. For purposes of illustration, FIG. 2B shows a cross section 225 associated with a single eye 245, but another optics block, separate from the optics block 118, provides altered image light to another eye of the user.

Additionally, in some embodiments, the microlens array 116 may also blur the image light that is concentrated toward the optics block 118. An image that is corrected for fixed pattern noise is then generated by the optics block 118 magnifying the blurred image light. In some embodiments, the optics block 118 may also correct for one or more additional optical errors (e.g., distortion, astigmatism, etc.).

FIG. 3A illustrates a cross section 300 of a sub-pixel 305 emitting light, according to an embodiment. The sub-pixel 305 includes an emission area 310 that emits light according to an emission distribution. The emission distribution has a primary emission axis 330 and off-axis boundaries 340 and 345. The primary emission axis 330 is a direction that the emission area 310 emits light with the most intensity. In cases where the emission distribution is Lambertian the intensity for an off-axis ray is based in part on the cosine of an angle subtending the off-axis ray and the primary emission axis 330. In this embodiment, the emission distribution has a solid angle 320 that subtends the off-axis boundaries 340 and 345. The emission distribution may be rotationally symmetric or rotationally asymmetric around the primary emission axis 330. Additionally, while this example shows the primary emission axis 330 being perpendicular to the emission area 310, in some embodiments, the primary emission axis 330 may be pointing in some other direction.

As the emissions distribution for various sub-pixels of the same color are generally going to be the same, it is apparent the location of the sub-pixel 305 affects have a strong effect regarding how much light makes it to an eye of the viewing user. For example, assuming the sub-pixel 305 is located in the center of the electronic display 115 light emitted near the off-axis boundaries 340 and 345 (e.g., for example around 70%) may not reach the viewing user and potentially cause stray-light in a HMD system. And the problem is exacerbated for sub-pixels on a periphery of the electronic display 115, as a larger portion of the emitted light does not make it to the optics block 118 (e.g., for example around 90%).

FIG. 3B illustrates a cross section 350 of the sub-pixel 305 and a corresponding microlens 360, according to an embodiment. The microlens 360 is a net positive lens that concentrates the emission distribution of the sub-pixel 305. Concentration of an emission distribution is the tightening of the emission distribution and the directing of the tightened emission distribution towards a target region (e.g., the optics block 118). A position of the microlens 360 relative to the emission area 310 is referred to as a microlens offset. The microlens offset is described as a position of a microlens optical axis relative to a corresponding sub-pixel centroid. A shape of the microlens 360 and the microlens offset adjust the solid angle 320 to an adjusted solid angle 370. In this embodiment, the adjusted solid angle 370 is less than the solid angle 320, which means that the emission distribution is more directed than that discussed above with regard to FIG. 3A.

Additionally, the shape of the micro-lens 360 and the microlens offset are designed to orient the primary emission axis 330 toward a specific direction. Accordingly, a shape of the micro-lens 360 and/or a microlens offset can be adjusted to generate a primary axis of emission along a particular direction. As an example, this emission direction may be approximately normal to the display surface for an on-axis sub-pixel position, but approach 30 degrees at the periphery of the display (still relative to the display normal vector).

FIG. 4 illustrates a cross section 400 of a directed display 405, according to an embodiment. In some embodiments, the directed display 405 is a component (e.g., directed display 112) of the VR headset 105. In alternate embodiments, the directed display 405 is part of some other HMD or other system that directs display light to a particular location.

The directed display 405 includes an electronic display element 407 and a microlens array 416. The electronic display element 407 is substantially similar to the electronic display element 235.

The electronic display element 407 includes a plurality of sub-pixels, the plurality including a sub-pixel 410A near a center portion of the electronic display element 407 and a sub-pixel 410B on a periphery of the electronic display element 407. The sub-pixels may be substantially similar to the sub-pixels 310 described above with references to FIGS. 3A and 3B. Each of the sub-pixels 410 emits light in a particular emission distribution. For simplicity, it is assumed that the emission distribution is the same regardless of sub-pixel color. However, in other embodiments, the emission distribution may vary based on, e.g., color of the emitting sub-pixel 410.

The microlens array 416 includes a plurality of microlenses that concentrate the light emitted from the electronic display element 407 towards a target region 440. The target region 440 is a region and/or component that receives the concentrated light. For example, the target region 440 may be an optics block (e.g., optics block 118), or more specifically the exit/entrance pupil of the optical blocks in a HMD, an eyebox (i.e., a region of space where a viewer's eye is located), some component of an HMD, etc. The plurality of microlenses includes a microlens 420A that is coupled to the sub-pixel 410A, and microlens 420B that is coupled to the sub-pixel 420B. To insure that the microlens array 416 does not affect the relative brightness between the sub pixels, the pitch of the microlenses needs to be similar to that of the sub-pixels. The microlens array 416 also needs to follow a few design rules:

The divergence of the beam needs to be large enough so to cover the solid angle collected by the eye. Considering an eye box dimension “EB” and assuming that the collimation optics have a focal length “F1,” the angle of emission out of the lens array needs to be larger than EB/F1 (full angle). If we now consider the physical dimension of the sub pixels “SP” and we assume that the sub-pixels are located at the focus of the lens array and those lenses have a focal length “F2,” then the angle of emission is given by SP/F2. Accordingly, the condition for the system to work is SP/F2>EB/F1. Numerical example can be an eye box of 10 mm, a collimating lens focal F2=40 mm and a sub pixel size SP=15 microns. For this example, the condition on the micro lens focal length is given by F2<SP*F1/EB=60 microns.

In some embodiments, a coating is placed on top of the OLED layers of the electronic display element 407 to minimize refractions caused due to the microlenses. Since that type of design requires very short distance from the pixels to the lenses, it is important to reduce the thickness of the stack so as to place the lenses as close as possible to the pixels. A potential problem, however is that OLED display usually uses relatively thick cover glass for the purpose of sealing. Some alternative solutions exist such as when the sealing is provided by thin coatings with thicknesses less than 10 microns.

For a given sub-pixel and corresponding microlens, a microlens offset and a shape of the microlens are designed based on a position of the given sub-pixel in the electronic display element 407. For the sub-pixels near the center of the electronic display 115 (e.g., microlens 420A) the shapes of the microlenses may have a flatter center (less curvature), but stronger curvature along the peripheries. For example, light emitted near off-axis boundaries is rather strongly bent by the microlens 420A toward a primary emission axis 430, whereas a much weaker bending occurs for light emitted near the primary emission axis 430.

In contrast, for sub-pixels that are near a periphery (e.g., sub-pixel 410B) of the electronic display element 407, the micolenses (e.g., microlens 410B) are shaped to bend the emitted light toward the target region 440. Additionally, the microlenses near the periphery of the electronic display 407 may have microlens offsets that facilitate light emitted from the emission area being incident on curved surfaces (stronger refraction). For example, the microlens 420B is clearly positioned differently relative to its corresponding sub-pixel 410B than the microlens 420A's position relative to its corresponding sub-pixel 410A. For a given microlens, an amount of microlens offset and a shape of the microlens are designed to concentrate light emitted from a corresponding sub-pixel toward the target region 440.

In addition, the optical design of the microlens as a function of radial or X/Y-axis position on the display can be a variable to allow further improvement and customization in the resulting system design. For instance, sub-pixel 410A may have a spherical shaped microlens with a radius defined by R, while sub-pixel 410B could have an aspherical shaped microlens with a radius of Y times R. This allows for both a microlens array that has the same lens properties repeated across the array (potentially easier to fabricate in mass quantities), or supports a microlens design that is optimized for its particular display coordinate (relative to the optical axis of the optics block 118).

Turning now to a discussion regarding embodiments of microlenses designed to diffuse (i.e., spread out) light emitted from the sub-pixels. In these embodiments, the microlenses concentrate the light emitted from the sub-pixels and/or pixels but also slightly diffuse the emitted light to jointly eliminate the ‘screen-door’ effect (dark space region between adjacent sub-pixels) and maintain the eyebox size. This results in a minimum blur diameter of the sub-pixel through the optics block 118, to generate the eyebox for the user, while also creating some apparent blur in the perceived image to fill in the dark space region (here blur is defined as a compensation to the fixed-pattern noise, defined also as ‘screen-door’ effect, that cannot be affected by the users visual accommodation system). A blur spot for a given sub-pixel is therefore a diffused image of a sub-pixel.

FIG. 5A illustrates a sub-pixel 520 coupled to a diffuser microlens 510, according to an embodiment. The diffuser microlens 510 has a microlens offset (optical axis relative to a corresponding sub-pixel centroid) and shape that concentrate light emitted from the sub-pixel 520. In this embodiment, the shape of the lens refers to the general curvature of an outer surface 530. The outer surface 530 includes a plurality of diffusing features 540. A diffusing feature blurs the light transmitted by the microlens 510. A diffusing feature 540 may be, e.g., a Fresnel structure, an engineered diffuser, an aspherical surface, a polynomial surface, a sinusoidal variance to a surface of the microlens 510 (e.g., the outer surface 530), some other feature that blurs light, or some combination thereof. The blurred image light helps allow the gain of the microlens structure to wash out the “screen-door” effect, such that any dark space region between sub-pixels is not visible to a viewing user, while maintaining at least a minimum eyebox size.

FIG. 5B illustrates the sub-pixel 520 coupled to a diffuser microlens 550 that includes a waveguide structure 555, according to an embodiment. The waveguide structure includes a waveguide entrance 565, a waveguide exit 567, and a confinement structure 570. The waveguide entrance 565 receives light from an emission area 560. The received light propagates within the confinement structure 570 until it reaches the waveguide exit 567. The confinement structure 570 is tapered such that light within the waveguide structure 555 is tightly confined near the emission area 560, but the confinement relaxes as the light moves toward the waveguide exit 567. This change in confinement allows a larger net increase in collected light (with rays near plus or minus 90 degrees relative to the display surface normal vector) while preventing high-angle cross-talk or stray light, and blurs the light emitted from the diffuser microlens 550, which again may be used to mitigate the screen-door effect.

FIG. 5C illustrates an example of the sub-pixel 520 coupled to a diffuser microlens 575 that includes the waveguide structure 555 and a plurality of diffusing features 540, according to an embodiment. In this example, the diffuser microlens 575 is substantially similar to the diffuser microlens 550 in FIG. 5B, except that the diffuser microlens 575 also includes a plurality of diffusing features 540 (e.g., as discussed above with regard to FIG. 5A) on the outer surface 530 of the diffusing microlens 575.

FIG. 5D illustrates another example of the sub-pixel 520 coupled to a diffuser microlens 580 including internal diffusing features 590, according to an embodiment. The diffuser microlens 580 includes a material 588 of a different index than that of the diffuser microlens 580, between the emission area 560 diffusing features 590 (i.e., a plurality of the diffusing features 540). In some embodiments the material 588 may be air, plastic polymer, a material having an index differing by at least 5% from the diffuser microlens 580, or some combination thereof. Accordingly, in this embodiment, the light is blurred by the plurality of diffusing features 590 prior to reaching the outer surface 530 of the diffuser microlens 580.

FIG. 5E illustrates a cross section of an electronic display element 407 coupled to a microlens array 505, according to one embodiment. The electronic display element 407 includes a plurality of sub-pixels 520, for example, three sub-pixels 520 are shown in FIG. 5E. The microlens array 505 includes a microlens array spacer 507 and a plurality of microlenses 582. The microlens array 505 and the electronic display element 407 are separated by an air gap 583. The microlens array spacer 507 is coupled to the electronic display element 407 using posts that provide mechanical support. The spacers can be in the form of pillars and be part of the microlens array structure so as to insure the correct distance to the display pixels. In the example embodiment depicted in FIG. 5E, each of the microlenses 582 is substantially similar to the diffuser microlens 510, except that the microlens 582 does not include a plurality of diffusing features 540 (e.g., as discussed above with regard to FIG. 5A) on the outer surface 530 of the microlens 582. Alternatively, the microlens 582 includes the plurality of diffusing features 540 on the outer surface 530 and would be identical to the diffusing microlens 510. The microlens 582 may have a microlens offset (optical axis relative to a corresponding sub-pixel centroid) and shape that concentrate light emitted from the sub-pixel 520. The microlens array spacer 507 is composed of the same material as that of the microlens 582. In alternate embodiments, the microlens array spacer 507 is composed of a material having an index of refraction within a threshold range of an index of refraction of the microlens 582. For example, the indices of refraction of the lens array spacer 507 and the microlens 582 may vary from each other by less than 5% (and in some cases may be the same). The dimension of the microlens array spacer 507 in a direction perpendicular to the viewable surface of the electronic display element 407 (i.e., a distance between the outer surface 530 and the edge of the microlens array 505 that is adjacent to the air gap 583) affects how well the electronic display element 407 may direct the emission distributions of sub-pixels 520 towards a target region. Example dimensions and pitch of the microlenses are identical to the pitch of the sub-pixels (e.g., in the range of 10 to 30 microns). Air gaps and spacers are typically designed such that the pixels are located close to the focal plane of the microlenses with a distance in the order of 50 to 200 microns.

FIG. 5F illustrates a cross section of an electronic display element 407 coupled to a microlens array 505, according to one embodiment. The coupling of the cross section of the electronic display element 407 with the microlens array 505 depicted in FIG. 5F is similar to that of the coupling described above in conjunction with FIG. 5E except that the microlens array 505 of FIG. 5F is placed on an inner surface 531 of the microlens array 505 of FIG. 5E. In FIG. 5F, the surface of the microlens array 505 that includes the microlens 582 is positioned closer to the electronic display element 407 (i.e., inner surface of the microlens array 505). The microlens array spacer 507 and the microlens 582 are same as described above in conjunction with FIG. 5E. The dimensions of the air gap 583 depicted in FIG. 5F may be different from that of the air gap 583 depicted in FIG. 5E to account for the curvature of the microlens 582 in FIG. 5F.

FIG. 5G illustrates a cross section of an electronic display element 407 coupled to a microlens array 505, according to one embodiment. The microlens array 505 includes a microlens array spacer 507 and a plurality of microlenses 592 that include a tapering structure, according to an embodiment. The tapering structure includes a tapering entrance 593 and a tapering exit 594. The tapering entrance 593 receives light from an emission area of the sub-pixel 520. The received light propagates within the tapering structure until it reaches the tapering exit 594. The tapering structure is tapered such that light within the structure is tightly confined near an emission area of a sub-pixel 520 and the confinement relaxes as the light moves toward the tapering exit 594. This change in confinement allows a larger net increase in collected light (with rays near plus or minus 90 degrees relative to the display surface normal vector) while preventing high-angle cross-talk or stray light, and blurs the light emitted from the microlens 592 similar to microlens 550 described above in conjunction with FIG. 5B, which may be used to mitigate the screen-door effect. Tapering structure can be fabricated by microlithography or by using replicated polymer structures.

FIG. 6A is an example array 600 of sub-pixels on the electronic display element 235, according to an embodiment. The example array 600 includes red sub-pixels 610, blue sub-pixels 620, and green sub-pixels 330. For example, the array 600 is portion of a PENTILE® display. A dark space region 640 separates each sub-pixel from one or more adjacent sub-pixels. The dark space region 640 is a portion of the array 600 that does not emit light, and may become visible to a user under certain circumstances (e.g., magnification) causing the screen-door effect that degrades image quality and the resulting VR or AR experience. As discussed above in conjunction with FIG. 2B, the optical block 118 includes one or more optical elements configured to magnify the blurred image light transmitted by the microlens array 116 to reduce fixed pattern noise so the dark space region 640 between the sub-pixels is not visible to the user. The microlens array 116 includes a plurality of diffusing microlenses that are configured to blur image light generated from each sub-pixel and the optics block 118 is configured to magnify the blurred image light. The amounts of blur and magnification for image light generated from different sub pixels are determined so adjacent blur spots in the corrected image light are large enough to mask the dark space region 640 between adjacent sub-pixels, while still allowing the image light from adjacent sub-pixels to be resolved by a user as image light from separate sub-pixels.

FIG. 6B is an example of image light emitted by an array of sub-pixels (e.g., array 600) and adjusted by the microlens array 116 and the optics block 118, according to an embodiment. As shown in FIG. 6B, each of the sub-pixels has an associated blur spot (combination of ray and diffraction properties). Specifically, the red sub-pixels 610 have a corresponding red blur spot 660, the blue sub-pixels 620 have a corresponding blue blur spot 670, and the green sub-pixels 630 have a corresponding green blur spot 680. A blur spot is an area filled with an image of a blurred sub-pixel. So long as a blur spot does not overlap with a point of maximum intensity of an adjacent blur spot, the two blur spots are resolvable as two adjacent sub-pixels. The shape of the blur spot is not necessarily a circle, but is rather an area including the blurred image of a sub-pixel. The microlenses in the microlens array 116 are configured to blur each sub-pixel so that after magnification by the optics block 118 the blur spots mask the dark space region 640 between adjacent sub-pixels.

FIG. 7A illustrates a cross-section of a directed display with a single microlens for each set of an example array of sub-pixels, according to one embodiment. In some embodiments, the directed display 705 is a component (e.g., directed display 112) of the VR headset 105. In alternate embodiments, the directed display 705 is part of some other HMD or other system that directs display light to a particular location.

FIG. 7A shows a cross-section of a directed display 705 including a set of sub-pixels 702 and a set of sub-pixels 704 coupled to a microlens 712A and a microlens 712B, respectively, according to an embodiment. The set of sub-pixels 702 includes sub-pixels 710A, 710B, and 710C, and the set of sub-pixels 704 includes sub-pixels 710D, 710E, and 710F. The sub-pixels of the two sets of sub-pixels may be configured to emit light at different wavelengths. In some embodiments, sub-pixels 712A and 712D may be configured as red sub-pixels, sub-pixels 712B and 712E may be configured as blue sub-pixels, and sub-pixels 712C and 712F may be configured as green sub-pixels. In some embodiments, FIG. 7A shows a single microlens coupled to three sub-pixels corresponding to red, blue, and green sub-pixels, where the three sub-pixels collectively represent one group pixel of the directed display 705. Alternatively, a single microlens may be coupled to each sub-pixel as discussed above in conjunction with FIG. 4.

In some embodiments, the dimensions of the microlens 712A are selected based on a sub-pixel pitch. For example, the diameter of the microlens 712A is selected to be same as a distance from one end of the sub-pixel 710A to the other end of sub-pixel 710C as depicted in FIG. 7A. Alternatively, the diameter of the microlens 712A is selected to be either larger than or smaller than the distance from one end of the sub-pixel 710A to the other end of sub-pixel 710C depicted in FIG. 7A. The emission distribution of the set of sub-pixels 702 has a primary emission axis 730 and off-axis boundaries 735 and 737. The primary emission axis 730 is a direction that the emission area of the set of sub-pixels 702 emits light with the most intensity. In this embodiment, the emission distribution has a solid angle 740 that subtends the off-axis boundaries 735 and 737. The emission distribution may be rotationally symmetric or rotationally asymmetric around the primary emission axis 730. Additionally, while this example shows the primary emission axis 730 being perpendicular to the emission area of the set of sub-pixels 702, in some embodiments, the primary emission axis 730 may be pointing in some other direction.

When a single microlens is coupled with three sub-pixels as depicted in FIG. 7A, the emission characteristics of light emitted by the three sub-pixels and passing through the microlens might result in a lower brightness than when a separate microlens is coupled with each sub-pixel (e.g., FIG. 4). For example, sub-pixel 710A emits light such that most of the light is emitted through the microlens 712A in a direction with a negative angle relative to the primary emission axis 730 in an XY Cartesian coordinate system 790, where the positive X-axis is along the primary emission axis 730 and the positive Y-axis is in an upward direction as shown in FIG. 7A. In the same example, sub-pixel 710C emits light such that most of the light is emitted through the microlens 712A in a direction with a positive angle relative to the primary emission axis 730 in the coordinate system 790. In the same example, sub-pixel 710B emits light such that most of the light is emitted through the microlens 712A in a direction that is along the X-axis of the XY coordinate system 790. For this example, the effective brightness of light emitted by the group of sub-pixels 710A, 710B, and 710C coupled to microlens 712A would be lower than if each of the sub-pixels were coupled to a separate microlens.

FIG. 7B shows a cross-section of a directed display 705 including a grouped set of sub-pixels 752 and a grouped set of sub-pixels 754 coupled to a microlens 712A and a microlens 712B, respectively, according to an embodiment. The grouped set of sub-pixels 752 includes sub-pixels 710A, 710B, and 710C, and the grouped set of sub-pixels 754 includes sub-pixels 710D, 710E, and 710F. The sets of grouped sub-pixels 752, 754, are sub-pixels that are grouped to improve the quality of image light incident upon a target region. In one example embodiment, the sub-pixels 710A, 710B, and 710C are positioned such that a dark space between two adjacent sub-pixels is reduced when compared with the dark space of sub-pixels depicted in FIG. 7A. For example, sub-pixel 710B is placed next to sub-pixel 710A such that there is effectively no dark space between the sub-pixels 710A and 710B (e.g., sub-pixels 710A and 710B abut each other). Likewise, sub-pixel 710C is placed next to sub-pixel 710B such that there is effectively no dark space between the sub-pixels 710B and 710C. FIG. 7B also shows the other grouped set of sub-pixels 710D, 710E, and 710F placed next to each other with effectively no dark space between the sub-pixels. In practice, with current Pentile OLED displays, the dimension of the dark area between sub-pixels is in the order of 20 to 30 microns. The spacing between each grouped set of sub-pixels 752, 754 may be the same or similar to the spacing between the set of sub-pixels 702 and the set of sub-pixels 704 discussed above with regard to FIG. 7A. For example, the distance between the sub-pixel 710B and sub-pixel 710E is same as the distance between those pixels in FIG. 7A. In other words, the sub-pixel placement on the directed display 705 is changed in FIG. 7B such that a pixel pitch between each set of sub-pixels (e.g., group of three sub-pixels) is same as that of the pixel pitch between each set of sub-pixels of FIG. 7A. At the same time, the sub-pixel pitch between two adjacent sub-pixels within a set of sub-pixels is reduced in FIG. 7B to improve the effective brightness of the emitted light. The emission distribution of the grouped set of sub-pixels 752 has a primary emission axis 750 and off-axis boundaries 745 and 747. In some embodiments, the primary emission axis 750 is same as the primary emission axis 730. The primary emission axis 750 is a direction that the emission area of the grouped set of sub-pixels 752 emits light with the most intensity.

In the example embodiment of FIG. 7B, the effective brightness of light emitted by the set of pixels is greater than that of the same set of pixels described above in conjunction with FIG. 7A. For example, sub-pixel 710A emits light such that most of the light is emitted through the microlens 712A at an angle relative to the primary emission axis 750 that is less than the angle corresponding to the sub-pixel 710A described in FIG. 7A but is still a negative angle relative to the primary emission axis 750. The light emitted by sub-pixel 710A in FIG. 7B has a smaller deviation from the primary emission axis 750 when compared with that of the light emitted by the same sub-pixel 710A in FIG. 7A. Similarly, sub-pixel 710C emits light such that most of the light is emitted through the microlens 722A at an angle that is less than an angle corresponding to the sub-pixel 710A described in FIG. 7A but is still a positive angle relative to the primary emission axis 750. For this example, the effective brightness of light emitted by the group of sub-pixels 710A, 710B, and 710C coupled to microlens 722A would be higher than that of the example depicted in FIG. 7A. In this embodiment where the dark space between two adjacent sub-pixels is reduced when compared with the dark space of sub-pixels depicted in FIG. 7A, the solid angle 760 of the emission distribution is smaller than the solid angle 740 corresponding to the set of sub-pixels 702 of FIG. 7A, which in turn reduces an amount of wasted light and improves the effective brightness of the emitted light.

In one embodiment, the grouping of the set of sub-pixels shown in FIG. 7B is implemented in two-dimensions. For example, the sub-pixels of the directed display 705 are in practice arranged as a two-dimensional pattern as shown in FIGS. 6A and 6B. An example grouping of the set of sub-pixels may include grouping of two or more sub-pixels and each such grouping may be coupled with a single microlens to improve the overall brightness of the directed display 705. For example, each grouping may include one red sub-pixel, one green sub-pixel, and one blue sub-pixel.

Additional Configuration Information

The foregoing description of the embodiments has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the patent rights to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the patent rights be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the patent rights, which is set forth in the following claims. 

What is claimed is:
 1. A head mounted display (HMD) comprising: an electronic display composed of a plurality of sub-pixels and each sub-pixel is configured to emit image light according to respective emission distribution; a microlens array coupled to the electronic display, the microlens array including a plurality of microlenses coupled to a microlens array spacer, the microlens array configured to concentrate the emission distributions of the sub-pixels to form concentrated image light and direct the concentrated image light towards a target region, wherein the microlens array is separated from a surface of the electronic display by an air gap, wherein the plurality of microlenses each have a respective shape, and the respective shapes of the plurality of microlenses vary with position of the plurality of microlenses relative to the electronic display such that each of the plurality of microlenses direct light toward the target region; and an optics block positioned in the target region, the optics block configured to direct the concentrated image light from the microlens array to an exit pupil of the HMD corresponding to a location of an eye of a user of the HMD.
 2. The HMD of claim 1, wherein the plurality of sub-pixels are divided into groups and each group forms a corresponding pixel, and each of the plurality of microlenses is aligned with a different pixel.
 3. The HMD of claim 1, wherein each of the plurality of microlenses is aligned with a different sub-pixel of the plurality of sub-pixels.
 4. The HMD of claim 1, wherein each respective shape of the respective shapes concentrates an emission distribution of a corresponding sub-pixel, the concentration causing a reduction in solid angle of the emission distribution and determines a direction of propagation of the concentrated image light from the plurality of microlenses.
 5. The HMD of claim 4, wherein some of the plurality of microlenses have an offset from a corresponding sub-pixel, and the offset is more for micolenses along a periphery of the electronic display than a microlens at a center of the display.
 6. The HMD of claim 1, wherein at least one microlens includes diffusing features on an outer surface of the microlens that reduces fixed pattern noise in the concentrated image light.
 7. The HMD of claim 1, wherein at least one microlens is a diffuser microlens that includes a waveguide structure, the waveguide structure comprising: a waveguide entrance configured to receive light from an emission area of the electronic display; a waveguide exit to direct light towards the target region; and a confinement structure that is tapered such that light within the waveguide structure is less confined at the waveguide exit than at the waveguide entrance.
 8. The HMD of claim 7, wherein the diffuser microlens includes diffusing features on an outer surface of the diffuser microlens that reduces fixed pattern noise in the concentrated image light.
 9. The HMD of claim 1, wherein at least one microlens is a diffuser microlens including internal diffusing features and another air gap separates the internal diffusing features from an emission area of a pixel of the electronic display.
 10. The HMD of claim 1, wherein the microlens array spacer separates the plurality of microlenses from the surface of the electronic display.
 11. The HMD of claim 1, wherein the plurality of microlenses are placed on an inner surface of the microlens array spacer facing the surface of the electronic display.
 12. The HMD of claim 1, wherein the plurality of microlenses are configured to blur image light and the optics block is configured to magnify blurred image light from the plurality of microlenses to produce a plurality of blur spots to mask a dark space region between adjacent sub-pixels of the electronic display.
 13. The HMD of claim 1, wherein each microlens corresponds to a set of two or more subpixels and a pixel pitch between each sub-pixel of a set of sub-pixels is less than a pixel pitch between sets of sub-pixels.
 14. A directed display comprising: an electronic display composed of a plurality of sub-pixels and each sub-pixel is configured to emit image light according to respective emission distribution; and a microlens array coupled to the electronic display, the microlens array including a plurality of microlenses coupled to a microlens array spacer, the microlens array configured to concentrate the emission distributions of the sub-pixels to form concentrated image light and direct the concentrated image light towards a target region, wherein the microlens array is separated from a surface of the electronic display by an air gap, wherein the plurality of microlenses each have a respective shape, and the respective shapes of the plurality of microlenses vary with position of the plurality of microlenses relative to the electronic display such that each of the plurality of microlenses direct light toward the target region.
 15. The directed display of claim 14, wherein the plurality of sub-pixels are divided into groups and each group forms a corresponding pixel, and each of the plurality of microlenses is aligned with a different pixel.
 16. The directed display of claim 14, wherein each of the plurality of microlenses is aligned with a different sub-pixel of the plurality of sub-pixels.
 17. The directed display of claim 14, wherein each respective shape of the respective shapes concentrates an emission distribution of a corresponding sub-pixel, the concentration causing a reduction in solid angle of the emission distribution and determines a direction of propagation of the concentrated image light from the plurality of microlenses.
 18. The directed display of claim 14, configured to operate as part of a head-mounted display. 